1. Field of the Invention
The present invention relates to a method for processing multimedia data in a multimedia database and a system therefor, and more particularly, to a method of searching and editing multimedia data and data related thereto and a system therefor.
2. Description of the Related Art
Large enterprises and self-governing communities having large-scale facilities such as electric power, gas and water maintain a great number of drawings illustrating these facilities. Maps and drawings managed in the form of paper have been accumulated in databases multimedia database by computers with capabilities in CAD techniques or multimedia processing techniques. Techniques on map/drawing information processing systems and CAD systems have been directed to investigate how multimedia data are efficiently inputted to the database and how such data are consistently managed.
However, prior art techniques are not appropriate for the case where a large number of figure data such as maps and drawings are to be managed. FIG. 8 is an example of a drawing illustrating a facility possessed by an enterprise or a self-governing community which manages large-scale facilities. A prior art technique will be explained based on this drawing.
One of the features of drawings and maps is that objects actually having a three-dimensional shape are expressed on a two-dimensional plane. For thus expressing three-dimensional information by two-dimensional information, attribute value data, for example, a depth or height, or the number of floors for a building or the like in a midtown area may be often used. A facility managed in the drawing of FIG. 8 may actually have a three-dimensional shape as shown in FIG. 9.
In FIG. 8, a fat line extending from left to right represents an underground cable line managed by an electric power company, while a line extending vertically a sewer pipe line managed by a waterworks company. A combination of a rectangle and a circle positioned on the left side of FIG. 8 represents a manhole for managing connection between the cable line portions. Numerals 10 and 20 are attribute value data of two portions of the cable line, which represent buried positions of the respective portions.
A combination of a rectangle and a plurality of smaller rectangles is data showing a sectional structure of the cable line. The cable line is typically composed of a bundle of electrical wires, and the sectional structure shows a method of forming the bundle. Generally, such sectional structure is managed in detail by a separate document. For example, each smaller section may be numbered so as to manage connection between the electrical wires on the both sides of the manhole. Thin lines are used to show data such as a sectional structure and depth (10 m, 20 m) at a variety of positions in correspondence to the cable line, whereby a buried state is readily verified by view. Middle lines other than those mentioned above represent roads in a similar manner to ordinary maps.
Drawings as mentioned above are managed, for example, by a drawing information processing system, so that shape, depth and section data are generated from the map representing each building or the like, as shown in FIG. 1. For simplicity, the prior art will be explained, with reference to FIG. 1, solely regarding the cable line in FIG. 8. A left part of FIG. 1 indicates display elements on the screen, while a right part of the same indicates objects corresponding to the respective display elements. For example, since the cable line in FIG. 8 is related with two kinds of data, i.e., a depth and a cross-sectional structure, there are required a drawing class, a depth class and a section class.
Since internal data of an object in the drawing class, i.e., a drawing object represent the cable line, data indicative of a line P.sub.0 P.sub.3, the coordinates of the points of which are P.sub.0 and P.sub.3, respectively, is registered in an internal data section of the drawing object. In an internal data section of an object in the section class, i.e., a section object, there are registered data representing a line P.sub.0 P.sub.1 or P.sub.1 P.sub.3 obtained by dividing the line P.sub.0 P.sub.3 at a changing point of the sectional structure and data representing a sectional structure. In an internal data section of an object in the depth class, i.e., a depth object, there are registered data representing a line P.sub.0 P.sub.2 obtained by dividing the line P.sub.0 P.sub.3 at a changing point and data 10 m or 20 m representing attribute values of the depths.
Methods for managing internal data such as those lines are also described in a method section for every object. A method for the drawing object includes a first method of managing (e.g. deletion, display and so on) internal data of the drawing object and second and third methods for managing internal data of other classes by an operation in the drawing object. The second method is a method of managing relation with the section objects and the third method is a method of managing relation with the depth objects. An example of handling internal data of an object in another class by operation results on the internal data of the drawing object may be movement of the cable line. This is because, when a sectional structure of the cable line is given by image data, it is necessary to modify a displayed position of the image data due to the movement of the cable line.
A drawing information processing system requires a search operation and an editing operation, and required editing functions are roughly divided into the following two:
(A1) A different class data modifying function, and PA1 (A2) A drawing data modifying function PA1 (B1) A value of internal data of an object specified by a selected point, and PA1 (B2) A range of the same internal data value,
Further, the different class data modifying function (A1) requires a function for modifying internal data of another object and a function for modifying a range related to the internal data of another object.
To achieve the search function and the editing function as mentioned above, it is necessary to display:
when the internal data are to be displayed upon search of the internal data or in the middle of editing the internal data. For visually indicating a range of the same internal data value to the user, generally a figure corresponding to the range is superimposed on a searched map or drawing and marked thereon. Such a figure for marking is not necessary when the searched original map or drawing is displayed. The number of figures necessary for marking in the course of a property data search operation depends on the number of related property data.
Conventionally, the marking technique has been achieved by providing a class for each of properties such as depth and section and registering figures for marking in every class, as shown in FIG. 1. In other words, the same figures for marking have been registered for each of a plurality of properties. For example, even if the shape is a line, the same figures are registered in the classes corresponding to the depth and section properties in the prior art example explained above. Therefore, when a depth object is to be modified, the internal data of the depth object are not registered as a line but as two lines divided at a changing point of the depth property data.
In the case where image data are managed by the section class as in the above-mentioned example, when a line cable movement operation is to be executed, it is necessary to propagate this operation to the other classes. In this case, a method for the above-mentioned operation is described in a method for managing a relation with the section class in the drawing class. Such prior art is shown, for example, by Reference 1, "New Approach to Regional Plans and Facility Management--Map Information Processing System WING" by Kasahaya and Tsuruya in a reference "PIXEL No. 18".
In a conventional system as mentioned above, since a single figure is registered in different classes, if data on a figure are modified, it is necessary to modify the same figure data registered in all of the other classes. An example of the class where a large number of modifications are needed for the same figure data may be a processing of simultaneously displaying separately managed maps showing adjacent regions. In this case, it is necessary to modify a coordinate system of respective maps for merging maps in different coordinate systems to a common coordinate system. With a conventional method of registering a single figure in respective classes, the merge operation is needed for the figure registered in the respective classes, incurring a problem that a huge amount of operations are required.
Also, the above-mentioned prior art has a large number of classes related to a single figure and hence is not appropriate to a system in which new classes need to be related to the figure after the system has been built. Specifically, relations with other classes are managed by the respective classes, so that if data in a class are to be deleted or added, corresponding modifications are required to related methods in the other classes.
When these map or drawing data are registered in a database of a drawing information processing system or a CAD system, it is desirable to utilize the database not only as a special database for expert sections but also as a general database for ordinary sections such as a planning section. For this purpose, it is often required to extract only the essence from the map or drawing data, conceal unnecessary detailed information and emphasize the essence. With this respect, conventionally, necessary data for the essence are determined and extracted from a search result by a person, and an explanation is given to a requester for better understanding. Thus, it is the same as a conventional information offer by way of paper, and no advantage has been obtained from an electrically systematic management of map and drawing information. Also, the prior art has not been intended to provide a digest function which is adapted to extract only necessary data from complicated and detailed map or drawing data and display the extracted information with an emphasis in accordance with importance thereof.
However, there are several examples of investigating a semantic digest function for map or drawing information, mainly led by the universities, as published in Reference 2, "Realization of Rough Sketch Generating Function in Map Information System" by Niwa et al. in Papers 4R-7 for the 38th Meeting of National Conference of Information Academy, and Reference 3, "Semantic Summarizing Function in Map Database" in Computer Science Investigation Report No. 6, pp. 1-10 by Kyushu University Large-size Computer Center.
For example, Reference 2 discloses a method of generating a rough sketch from a departure point to a destination. In other methods, a navigational route is found from a whole map by a navigational searching algorithm, and a rough sketch is generated by investigating intersections along respective roads, with the navigation as the center, and adding roads from the intersections to the adjacent intersections, or roads in a town block including the navigation, and facilities and place names from the respective intersections.
On the other hand, Reference 3 proposes a control for automatically thinning out landform, shoreline and display characters so as to conform to a display scale and prevent superimposed characters when a rough sketch is generated from a map database having map or drawing data including a detailed landform, shoreline, display characters and so on.
However, in the method shown by the above-mentioned Reference 2, it is supposed that coordinate data indicative of a road and a shape of a building, symbols representing a shrine, a bank and so on and texts for display are uniformly described. Therefore, for generating a rough map, it is necessary to perform an navigation searching operation and a search operation within a near range for all elements of map or drawing data in the database. For this reason, it takes a long time to generate a rough map. Also, a rough map generated by this system is merely a rough sketch which principally shows roads in the same scale, wherein neither important elements or media are shown in detail, nor remaining elements are summarized according to importance.
The method of Reference 3 also supposes that map data are uniformly stored in the database. It is therefore necessary to repeatedly execute a geometric operation for automatically thinning out detailed data according to a scale and a lay-out operation for optimally positioning a map without superimposing displayed characters each time a rough map is generated. Thus, as a database is larger, an operating time therefore becomes extremely long. Further, a rough sketch generated by this method is a mere thinned-out sketch having the same scale wherein neither important shapes are shown in detail, nor the remaining parts are summarized according to importance.
Thus, the prior art implies operational problems caused by a difference in the semantic structure of the respective media for automatically generating a rough map or a guiding map. For example, a multimedia database structure for a drawing information processing system shows a semantic structure of a map generally drawn on a scale of 1/25000 which is not adapted for a semantic structure of a guiding map. Therefore, a variety of special media processing programs are required for merging maps showing necessary adjacent regions, changing a scale and so on to adapt for a media structure for a guiding map. Generally, a semantic structure of media (hereinafter simply called "the user model") requested by the user as an object to be processed is often different from a semantic structure of existing multimedia databases, and therefore if such difference is dealt with special programs, it will be required to develop a huge number of application programs.